Multiplex pulse communication system



May 23, 1950 H. Q. PETERSON MULTIPLEX PULSEl COMMUNICATION SYSTEM '7Sheets-Sheet Filed Nov. 9. 1944 EEEEEE NNRSN I INVENTOR 5f/Pa d Afri/mamATTORN EY MULTIPLEX PULSE COMMUNICATION SYSTEM ed 210V. 9, 1944 '7Sheets-Sheet 2 NNNNNN OR BY )f/wvm,

ATTORNEY May 23, 1950 H. o. PETERSON 2,508,620

MULTIPLEX PULSE COMMUNICATION SYSTEM Filed Nov. 9, 1944 '7 Sheets-Sheet5 nm WE ok +ll. lw. wire...

May 23, 1950 H. o. PETERSON MULTIPLEX PULSE COMMUNICATION SYSTEM 7Sheets-Sheet 4 Filed Nov. 9, 1944 itouantl' INVENTOR /oza 0. /frf/Pfo/v.BY f y /wvw ATTORNEY May 23, 1950 H. o. PETERSON 2,508,620

' MULTIPLEX PULSE COMMUNICATION SYSTEM Filed Nov. 1944 7 sheets-sheet 51 .c. TVE1 X35 1 bci. T C 537 1 he. T :l 47

1 bf. Tcl 746 ATTO RN EY May 23, 1950 H. o. PETERSON 2,508,520

' MULTIPLEX PULSE COMMUNICATION SYSTEM Filed Nov. 9, 1944 '7Sheets-Sheet 6 1:17a. T E64M MM 1 .7d. T H1 M T331. e. 6,0/ n l nAlNvl-:NTOR Afl/F040 d. Eff-WMM ATTOR N EY May 23, 1950 H. o. PETERsoN2,508,620

MULTIPLEX PULSE COMMUNICATION SYSTEM Filed Nov. 9, 1944 7 Sheets-Sheet 7BY gw ATTORN EY Patented May 23, 1950 MULTIPLEX PULSE. COMIVIUNIGATIONSYSTEM Harold O. Peterson,j Riverhead,- N. Y., assiimor to RadioCorporation of America, a. corporation oi Delaware Application November9, 1h44, Serial No... 562,618'.

(Cl. 25o-9.)

1Q Claims.

The present. inventicnfcemurises a multiplex type f .pulse ccmmuhicatichsystem. haring means. for synchronous commutation. cf. the variouschannels so. that each channel successively controls the transmissicnofenergy from. a transmitter to a receiyer.

ForA a given channel. the. number of pulses transmitted nerl .secondmust he greater than the highest signaling frequency. '.lhus.. icrtransmission of telephone signal. frequencies up t0 about 3.0.0.0cycles. it, would he desirable te trans: mit at least. about. 10.0.0.0.pulses every second icl: each channel. Hence. if seven. telephone,transmining ,channels are to. b e employed.. it. would he. required totransmit at .least 70.0.9.0. pulses per second. Thel .space between thepulses Qi. One channel would be divided into. time. intervals. each oneor which would be used by Que ci. the signalling channels. It is also..desirehle. t0. trans mit a synchronizing signal whereby theCQhitllllltation means. at the. receiver can be kept step with. the.channel sequence at. the transmitter. This. synchronizing signalwduld,of course., he in addition to the intielligenceV tran sin itj-,hingJpulses in the various channels..

In the embodiment of the invention herein described. the pulses each.channel of, the transmitting .syst-.en are modulated in` phase by thesignal.. The. pulses therefore can be. made. cuite, short cchinared. tethe time. intervals between. them. and they can be c-f. constant. widthand amplitude.. which; are conditions. favorable tdefcie..operation-.with certain tyres ci transrntteijs. The time duration ofthe transmitted pulses will depend upon the number ofl channelsemplcyed. und the number. 0f pulses for each channel.. Thus... if.;there ereseveh channels each. transmitting 110,000 pulsespersecond, and,there are. also transmitted synchronizingV pulses, the pulses may eachhave a duration of one micro.- secohd., for example. and be. phasemodulated =iglus andv minus 18?, so that, the pulses in each channel mayvary, in. phase. over a range cfv 3.6.o at theV channel. frequency of10,000pl1lses per, second. The timing of the pulsesin the differentchannels at the transmitter is so arrangedV that av pulse is transmittedwhen an alternating cur.- rent wave passesl through zero amplitude in.one direction. An artificial line` at the transmitter common to all ofthe channels xes` the phase otthe pulse in each. channel relative tothepulses ill Uhefcther. channels. for. euch cycle 0f operation orframe. At the receiver, the received. pulses cf: variable.- nhese are.converted. to. variable width uiilsesflwhich are. then...uti1.i2ed invan integrating device. An. artificial line. is lalso used at the receiver similar to. theorie lat the transmitter for i-lxing.- the )chestLof the, pulses. in. the different receiving channels..

A more detailed description of the invention follows in cohiunctionwith.the drawing, wherein:

Fig... 1, illustrates the transmitting system with oneA of the. channelsshown in. detail.;

Figs. .2a. 2b, 2c. 3 andeare graphs which ex'- lillain. the Qperaton. ofthe. transmitter.; Figs. 5a andl 5113.taken together, illustrate thereceiving system with one,..channel and. thesynchronizing means shown indetail; Figs. 6a tc ef. and Figs. is to. '1f are graphs whichexglaintheoperation. of the receiving sys..- tem; and i Fig. 8illustrates an. alternative detail which may beI used in the receiversynchronizing system.

Referring toFig.. 1,! there is. shown a pulse type of multiplex.transmitting, system with one of the hannelsshownin detail. Except forthe. use. of generator l., vacuum tube' 2articia1 linev 3, radio pulsetransmitter la and its output.y antenna I'S, which are common to, all.of` the channels,4 similar equipment appears. in. each.. of thechannels. Generator l. is, a, source of periodically recurring Waves;for example..L sine. Waves which. are. gen.- erated preferably atl a.very, constant frequency. The, sinusoidal output of thesine. Wai/. e.generator lI isV amplinedin. screen, gridvacuum tube ampli.- er. 2 andthen impressed on multfsection articial line 3 at. terminal 4'., If the4pulse frequency ofy each channel ischosen to be 10,000 pulsesper second,then. generator l. wouldhave a frequency of. 10,000 cycles per second.Artificial line 3 con.- sistsv of' a plurality of seriesr and shuntelements. Each section oi this artificial line introduces phase delay sothat the phase of the alternating currQIiiLWal/e at terminal''i's.delayed' withrespect to the phase, ofq the alternating current. wave atterminal' d; Likewise,r alternating current waves at termi'nal's..t',`7..; 8, 9; l]I, lili and' I2 are succes*- sively more delayed in phase.,The amountof thisdelay, ofeachsectloncan. be definitely det'erminad byvtheelectrical constants of the series and shunt. elements ofy the line3. known .cir-cuit'. means, than the line a are available fornroducinaxedamounts of'phase delay.; for. example therecan be employed'anumber oi phase. rotatursied in parallel',P Whose adjustments are .setto gil/.ej adilerentoutput phase fromeach.

InFig, 1 the alternating Current Wave appear.- ing. attermlnall is.amplified in aY vacuum tube V|3 andappearsintunedicircut'.,Il.; Thephase of the Veflterriaung. current voltage of. tuned' circuit lill' isOther Well 3 modulated by means of a pair of push-pull connectedreactance vacuum tubes I5 whose grids are coupled to an amplier I6, inturn coupled to a microphone M upon which the speech waves areimpressed. For a more detailed description of the operation of thepush-pull reactance tubes I5, reference is made to Usselman Patent2,342,708 (Fig. 2 thereof particularly), granted February 29, 1944. Theterminals 5 to I0, inclusive, shown on artincial line 3 are eachconnected to other vacuum tubes I3 whose outputs are treated in the samemanner as the channel associated with lead 4 and shown in detail in Fig.l. The sine wave output of tuned circuit I4 is passed by lead 200 to alimiter Il where it is converted into a clipped wave form, such as shownin Fig. 2a. The current of the wave form of Fig. 2a is passed through atransformer primary 20 which results in a secondary voltage in winding2| having a shape such as shown in Fig. 2b. The pulse transmitter I8 isso arranged that the negative voltage pulses shown in Fig. 2b have noeect on the transmitter output. The transmitter output from apparatus I8is fed into antenna I9 and is represented in Fig. 2c which shows a pulseof radio frequency energy. Pulse transmitter I8 can be any kind of pulsetransmitter which is controlled by an incoming pulse 'of suitablepolarity and which is normally not sending but is made to send radiofrequency energy upon receipt of an incoming pulse. This transmitter caninclude a flip-nop or a multivibrator type of circuit.

Circuits from the transformers 20, 2I of the other channels of themultiplex system are also introduced into the pulse transmitter I8, asshown, so that a short pulse of radio frequency energy istransmitted'each time transmitter I8 receives a short pulse of positive(unidirectional) voltage from any channel. Thus, the voltage appearingat terminals 5, l, 0, 9 and I0, representative of the alternatingcurrent waves from the other channels, may likewise be converted intophase modulated pulses for each of which the transmitter I8 will radiatea short pulse of radio frequency energy. The voltages at terminals IIand I2 on the artificial line 1? are used -to transmit two unmodulatedpulses which are spaced close together and which are to be used at thereceiver for synchronizing the commutation of the receiver. Terminals toI0, inclusive, .on articial line 3 are connected to different channelseach of which includes a tube I3, apparatus I4, I5, I0, II, 20, 2l, anda microphone M. Terminals II and I2 online 3 are separately connected tothe pulse transmitter I8 through separate paths each of which includesonly an amplifler tube and a limiter.

Fig. 3 illustrates the phases of the voltages on terminals 4 to I2,inclusive. These are used to control the timing of the radio frequencypulses in the manner illustrated in Fig. 4. In Fig. 4, pulses I to '1,inclusive, may each have their phases modulated by the signal over therange illustrated as The two pulses S, S which are shown closely spacedare the synchronizing pulses above mentioned. It should be noted thatpulses I to l, inclusive, and the synchronizing pulses S, S occur at thetime the alternating current waves of Fig. 3 (which are similarlylabeled except for the prime designations) pass in one direction throughzero amplitude. Thus, in the system as here shown, each cycle cf thepulse frequency oscillator I causes nine short pulses to be radiatedbythe pulse transmitter I8. Seven of these are used for signaling andtwo for synchronizing purposes. If the frequency of oscillator I is10,000 cycles per second, it will be evident that there are thereforetransmitted 90,000 pulses per second from the multiplex transmitter.Each of the pulses I to l', inclusive, in Fig. 4 will serve to transmitan independent message over a signaling channel. As described above,these pulses may each have a duration of one microsecond and be phasemodulated plus and minus 18 so that the pulses in each channel may varyin phase over a range of 36 at the channel frequency of 10,000 pulsesper second.

Fig. 5a represents one embodiment of a receiving system for use with themultiplex transmitter of Fig. 1. The radio frequency signal is receivedon a more or less conventional superheterodyne radio receiver 2I0 havinga receiving antenna ISS, as shown. In this receiver, the signal which isrectified at 202 appears as a direct current pulse which may be passedthrough a threshold limiter-clipper 204 which operates to eliminate anynoise between pulses, which noise lies below a predetermined value. Thislimiterclipper device also prevents the output pulses from exceeding apredetermined value. This device can serve to eliminate from the signalall amplitude variation due to noise if the peak pulse amplitude exceedsthe peak noise amplitude by at least 6 db. Such a clipper is sometimesreferred to as a top and bottom limiter because it removes noise andvariations above and below certain limits. A local oscillator I02 ofperiodically recurring waves, for example sine waves, serves to time thereception of the various channels. The phasing of the control wave forthe various channels is determined by an articial line 3' in the samemanner as described for the transmitter of Fig. l. Line 3 is similar toline 3 at the transmitter part of the system. Assuming that the pulsefrequency of a generator is 10,000 pulses per second, oscillator |02 ismade to have a frequency of 5,000 cycles per second. The reason formaking the oscillator frequency one-half of the oscillation frequencywill appear later.

The alternating current wave from the oscillator I02 is amplified invacuum tube 30 and its output appearing in transformer 3l is representedby Fig. 6a. When this is rectified by the full wave rectifier 32, thereis obtained in the load resistance 33 a wave having the shape shown inFig. 6b. The flow of current through resistance 33' develops a voltagewhich biases the tube 34 to cut-olf. It will be noted that this wave ofFig. 6b approaches zero voltage two times for each cycle of thealternating current wave generator |02. E1 in Fig. 6b represents thethreshold or cut-off value for tube 3ft. This pulse of current resultsin a negative pulse of voltage across resistor 35, as shown in Fig. 6d,and this negative pulse is transmitted to the grid of vacuum tube 38which causes the tube 38 to stop drawing plate current. The currentpulse through resistor 35 is represented in Fig. 6c.

Tubes 38 and 39 together with their associated circuit elements operatein a well known manner. This circuit detail is sometimes referred to asthe Finch locking circuit and is described in more detail in UnitedStates Patent No. 1,844,950, granted to J. L. Finch February 16, 1932.Locking circuit 38, 39 consists essentially of two vacuum tubes whichhave their yplates and grids resistively interconnected in such mannerthat the apparatus has two degrees of electrical stability.`

These devices are unstable when both are drawing current but stable whenone tube is drawing current and the other tube blocked or prevented frompassing current. The change from one condition of stable equilibrium,such as when device 38 is blocked and device 30 passing, to the othercondition when device 89 is blocked and device 38 is passing, is causedby the presence of'a suitable predetermined potential on the grids. Tube39 continues to draw plate current until a negative limited and clippedpulse is received from the radio receiver 2li! through lead 205 andcoupling condenser d8, at which time tube 39 ceases to draw current andtube 38 commences drawing current. Succeeding negati-ve pulses from thereceiver '2i have no effect on the circuit as long as tube 30 is alreadyblocked or cut-off.

By reference to Fig. 6i, it will be noted that the length of time duringwhich tube 39 draws current will depend upon the time interval betweenthe locally generated pulses from tube 34 (illustrated by the voltagepulse E37 in Fig. 6d)

and a next following negative pulse a. from the receiver obtained overlead 285. Note Fig. 6e. The pulses a.' to g shown in Fig 6e representthe seven pulses consecutively received from the seven channels. rihesepulses a to g in lead 205 build up a voltage across resistor l asrepresented by E'll in Fig. 6e. The angle in Fig. 6e represents therange over which the pulses in the incoming channels may be modulated.It should be noted that the locking circuit 38, 39 has converted thevariable phase input pulse from the receiver to a variable width outputpulse (Fig. (if) which is used in integrating tube and thence monitoredin headphones 54.

Referring to Fig. 7a, there is shown the voltage wave derived fromartificial line 3 amplified in vacuum tube 5t and appearing intransformer 56. This voltage wave of Fig. 7a is rectified in the fullwave rectifier 5i. In this case a direct current bias is introduced bypotentiometer 50 in such va manner that the rectifier 5l does not drawcurrent until the alternating current value exceeds a preset leveldetermined by the setting of 59. This results in a time interval N shownin Fig. 7b, during which no current'flows in resistor 58 in therectifier circuit. During this time interval in which no current ows inresistor 58, vacuum tube e0 is made to conduct current, providing the #3grid of tube 00 is also properly biased. The direct current bias of the#3 grid of tube 60 is set to such a value by bias potential source -Cthat no plate current flows in tube 60 except when a positive pulse isreceived through coupling `condenser 8|. This positive pulse may beproduced by the negative receiver signal pulses introduced at the gridof tube 'I9 through coupling condenser f8 from lead 205. It is producedby virtue of the negative pulse on lead 205 reducing the flow of currentin tube 19 and causing the anode voltage on this tube 'I9 to rise.rFhus, it will be seen that vacuum tube transmits nothing except duringtimes when there is zero bias on the #l grid (when rectifier 5l isnon-conducting) and a positive pulse on the #3 grid. Tube vmay thereforebe referred to as a gate or gating tube, sometimes referred to as ashutterJ This gating tube 00 supplies negative pulses to tube 82. Whenthe phase cf the oscillator |02 is approximately correct, the voltage onthe #l grid of tube 60 will be zero at such time that both of theclosely spaced synchronizing pulses received by the apparatus will beeifective in causing'two closely spaced positive pulses represented by'Fig. "Ic to appear on the grid on the'following. tube 62.

This tube 62 and its associated elements con'- stitute a countingcircuit timer.V In this counting circuit timer, each positive pulse addsan increment of voltage appearing across condenser 68. The legend E68(Fig. 7d) illustrates how the two positive pulses from E64 add toproduce a resultant triggering voltage on condenser 68. When thisvoltageexceeds a preset value, a blocking oscillator 1|, l2 generates apulse and at the same time discharges condenserl 68. A slow dischargecircuit 69, I0 has been added to dissipate charges which are spaced atintervals considerably greater than the interval between the twosynchronizing pulses. Thus, two closely spaced pulses introduced in thecounter circuit produce a single pulse in the plate circuit of tubeY 'l5(lead 206), which may be represented by the: showing of Fig. 7e. Fig. 7eshows the voltage built up across the resistor |0| (Fig. 5b) It will beseen that the counter circuit is essentially an integrating device orfrequency divider wherein an accumulating charge on the condenser 68eventually achieves a critical voltage that initiates Aa discharge cyclewhich discharges' the condenser preparatory to the next integrating orcountercycle. In the manner similar to that above' described for tube60, two-other tubes 82 and 83 are-caused to serve as gates or shuttersfor the pulse transmitted over lead 206 bythe counter circuit timer.These two gates are phased to operate at `'slightly dierent times, asillustrated in'Fig. 7j. If the pulse from vthe counter circuit timeroccurs at exactly the correct time, it will occur equally in th'etwogating tube outputs'which feed through transformers Si and 9'1- intorectiers Stand` 98 which have their load circuits at series opposition.Hence, when the pulse from the counter Vcircuit timer appears equallyat'the two gating tubes 82 and 83, there will be zero rvoltage appliedthrough connection |00 to the AFC circuit 208 controlling the frequencyof oscillator |02. However, if the pulse shown` in Fig. 7e is slightlydisplaced, it will appear more in one gate 82y or 83` than inthe othergate 83 or 82, and therefore result in a direct current voltage'beingapplied to theAFC circuit 208 in such manner as to make the'p'roperadjustment of the frequency of the oscillator |02. The AFC circuit288may be a motor which is controlled by the voltage'iri lead |00Aand-whose rotatable armature is linked to variable con-` denserinoscillator |02. I The slight phase displacementl necessary in thetimingof gates A60, 82 and 83-may be adjusted by means of the tuningcondensers in shunt with the *primaries -of transformers `50, 85 and-90. The voltage fed to the rectiers, 9| are those made'to differslightly in phase to achieve the results'shown in Fig. 7i.

Fig. 8 shows another detail'circuit whereby the pulse fromthecountercircuit-timer may be combinedwith the 'total frequency voltage derivedfrom oscillator |02'through a. frequency doubler |03 in such manner astoproduce ay synchronizing control voltage for the AFC circuit 208. Itshould be noted that the output of the frequency'doubleris supplied vialead |04 in pushpush to the diodes |05 and |06, whereas the pulses fromythe counter are supplied via transformer |01'to the same device inpush-pull. For` amore detailed description of the diode circuitarrangementof Fig. 8, reference is made tothe television` receivernsynchronizing 'circuity 'de-- 1 scribed by Wendt and `fredendali in theProceedings of the IRE for January, i943, pages '7-15, inclusive. Y

What is claimed is:

l. A pulse type multiplex communication system comprising an antennasystem and a plurality of channels coupled to said antenna system, anarticial line having a plurality of electrical sections in series, asource of alternating current waves coupled to said line, connectionsfrom said channels to different sections on said line, Whereby said linesupplies said channels With the Waves from said source at relativelydiiierent phases, each of said channels including apparatus forproducing pulses of energy from said Waves, the pulse duration of whichis short compared to the time interval between them, Asaid apparatus ineach channel including a tuned circuit producing a sinusoidal outputWave and a limiter coupled to said tuned circuit, and push-pullconnected reactance tube apparatus in each channel coupled to the tunedcircuit in that channel for modulating the timing of the pulses producedin that channel.

2. In a radio communication system, a plurality of transmitting channelseach having modulation equipment, a common source of periodicallyrecurring constant frequency sine waves for all of said channels, atransmissionline circuit coupled to said source and having connectionsfrom diiierent points located progressively along said line to differenttransmitting channels, to thereby supply said channels with said Wavesat diierent phases, means in each channel for converting said waves toconstant width pulses which are short compared to the time intervalsbetween them, said means including a tuned circuit for producing a sinewave output, a limiter coupled to said tuned circuit, and a pulsetransformer coupled tothe output oi said limiter; and a pulse radiotransmitter coupled to the outputs of said channels and controlled bythe pulses produced in said channels.

3. The method of multi-channel communication which includes the steps ofsupplying the diierent channels with alternating current voltage wavesof the same frequency but of different relative phases, modulating thephase of said alternating `current Waves in said channels independentlyof lone another in accordance with 1 diierent signals, separatelylimiting the modulated alternating current waves in said channels, andproducing from said Waves in said channels pulses of energy when saidWaves pass in only one direction through Vzero amplitude.

4. A pulse type multiplex communication system comprising transmittingapparatus and a plurality of intelligence carrying channels andasynchronizing circuit coupled at one end to said apparatus, atransmission line having a plurality of series connected sections, asource of periodically recurring constant frequency waves coupled to apoint on said multi-section transmission line, connections from theother ends of said channels and'from the other end of said synchronizingcircuit to diierent sections on said line progressively removed fromsaid point, whereby the phases of the recurring waves supplied to saidchannels are diilerent, means in each intelligence carrying channel forproducing pulses of energy from said waves and for modulating the timingof said pulses Within predetermined limits, and means in saidsynchronizing circuit for producing a pulse of energy from said Waves, aremotely located receiving .system` .i11-

`cluding a plurality of channels corresponding in number to the channelsat the location of the transmitter and also a synchronizing circuit,said receiving system including a multi-section transmission linesimilar to the line at the transmitter and a source of periodicallyrecurring waves of a frequency equal to half the pulse repetition ratefor each transmitter channel coupled to said line at the receiver, andconnections from the receiver channels and from said synchronizingcircuit to different sections of said last line to thereby receive fromsaid line recurring Waves with relatively different phases, means forsupplying the receiver channels and said synchronizing circuit with thepulses received by said receiving system, and an automatic frequencycontrol circuit coupled between said source of periodically recurringWaves at said receiving system and said last synchronizing circuit.

5. The method of multiplex transmission which includes generating anumber of time displaced sinusoidal waves of like frequency, phasemodulating each sinusoidal wave with a different signal, generating ahigh frequency carrier, de-4 riving unidirectional current pulses oflikepolarity from each of the phase modulated Waves, and modulating thecarrier with said derived pulses.

6. The method of multi-channel communication which includes the steps ofsupplying the different channels with alternating current voltage wavesof the same frequency but which are displaced in time, modulating theinstantaneous frequency of said alternating current waves in saidchannels independently of one another in accordance with differentsignals, producing pulses of undirectional current in said channels fromsaid modulated Waves, and utilizing only pulses of predeterminedpolarity in said channels to produce pulses of radio frequency energy.

'7. A pulse type multiplex communication system comprising transmittingapparatus and a plurality of intelligence carrying channels and aplurality of synchronizing circuits coupled at one end to saidapparatus, a source of periodically recurring constant irequency Wavescou-Y pled to a transmission line having a plurality of seriallyarranged sections, connections from the other ends of said channels andfrom the other endsv of said synchronizing circuits to differentsections on said line, whereby the phases of the recurring Wavessupplied to said channels and to. said synchronizing circuits arediierent, the time delay between adjacent sections connected to saidchannels being longer than the time delay between sections connected tosaid synchronizing circuits for a wave traveling over said line, meansin each channel for producing pulses of energy from said Waves and formodulating the timing of said pulses Within predetermined limita,

means in each synchronizing circuit for producing a pulse of energy, aremotely located receiving system including a plurality of channelscorresponding in number to the channels at the location of thetransmitter, said receiving system including a multi-sectiontransmission line similar to the line at the transmitter, a source ofperiodically recurring constant frequency Waves coupled to said line atthe receiver, and connections from the receiver channels to diierentsections of said last line, to thereby receive from said line recurringwaves with relatively different phases, only a single synchronizingcircuit at said receiver coupled to a dinerent section on said line thanthose sections to which the receiver g channels are coupled, and meansfor` supplying the receiver channels and the synchronizing circuit Withthe pulses received by said receiving system.

8. A pulse type multiplex communication system comprising transmittingapparatus and a plurality of intelligence carrying channels and asynchronizing circuit coupled at one end to said apparatus, atransmission line having a plurality of series connected sections, asource of periodically recurring constant frequency waves coupled to apoint on said multi-section transmission line, connections from theother ends ofy said channels and from the other end of saidsynchronizing circuit to diierent sections on said line progressivelyremoved from said point, Whereby the phases of the recurring wavessupplied to. said channels are different, means in each intelligencecarrying channel for producing pulses of energy from said Waves and formodulating the timing of said pulses with predetermined limits, andmeans in said synchronizing circuit for producing a pulse of energy fromsaid Waves, a remotely located receiving system including a plurality ofchannels corresponding in number to the channels at the location of thetransmitter and also a synchronizing circuit, said receiving systemincluding a multisection transmission line similar to the line at thetransmitter and a source of periodically recurring Waves of a frequencyequal to half the pulse repetition rate for each transmitter channelcoupled to said line at the receiver, and connections from the receiverchannels and from said synchronizing circuit to diierent sections ofsaid last line to thereby receive from said line recurring Waves withrelatively diierent phases, and means for supplying the receiverchannels and said synchronizing circuit with the pulses received by saidreceiving system, said synchronizing circuit at the receiver includingmeans responsive to the phase difference between a Wave representativeof the received synchronizing pulse and a Wave from said transmissionline at said receiver for automatically controlling the frequency of thesource of recurring Waves at the receiver, said last means having a pairof connections to different points on said line at the receiver andanother connection to a frequency controlling element for said source ofrecurring Waves at the receiver.

9. A pulse multiplex system comprising a source of recurring waves,means for abstracting from said source a plurality of time displacedsinusoiclal Waves of like frequency, means for modulating the phases ofdifferent ones of said plurality of time displaced sinusoidal waves withdifferent signals, means for deriving unidirectional current pulses oflike polarity from the different phase modulated Waves, means forgenerating a high frequency carrier Wave, and means for modulating saidcarrier wave with said derived pulses.

l0. The method of multi-channel communication which includes the stepsof supplying a pair of diiierent channels with recurring waves ofvarying amplitude and of the same frequency so phased that when one Wavein one channel is passing through zero amplitude the other Wave is atmaximum amplitude, producing from said Waves in said channels pulses ofenergy When said Waves pass through zero amplitude, and modulating saidpulses independently of one another.

HAROLD O. PETERSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,510,792 Merritt Oct. 7, 19241,802,745 Whitaker Apr. 28, 1931 1,979,463 Goshaw Nov. 6, 1934 2,048,081Riggs July 21, 1936 2,086,918 Luck July 13, 1937 2,113,214 Luck Apr. 5,1938 2,172,354 Blumlein Sept. 12, 1939 2,199,634 Koch May 7, 19402,209,395 Fitch July 30, 1940 2,213,941 Peterson Sept. 3, 1940 2,215,776Barnard Sept. 24, 1940 2,262,838 De Loraine et al. Nov. 18, 19412,352,634 Hull July 4, 1944 2,363,062 Hartley Nov. 21, 1944 2,414,265Lawson Jan. 14, 1947 2,423,466 Peterson July 8, 1947 2,429,608Chatterjea et al. Oct. 28, 1947 FOREIGN PATENTS Number Country Date118,054 Australia Jan. 20, 1944

